Composite material and method for producing composite material

ABSTRACT

A composite material including a first porous metal body having a three-dimensional mesh-like skeleton, a second porous metal body having a three-dimensional mesh-like skeleton, and a bonding portion formed by entanglement of the skeleton of the first porous metal body and the skeleton of the second porous metal body. The porosity of the first porous metal body may be different from the porosity of the second porous metal body.

TECHNICAL FIELD

The present invention relates to a composite material, in which porous metal bodies are bonded to each other, and a method for producing the composite material.

BACKGROUND ART

In recent years, porous metal bodies have attracted attention in the trend toward weight reduction of electronic equipment, automobiles, and the like. In the case where a metal material has a porous structure, a very high degree of lightness can be realized. In addition, the porous metal body has a large specific surface area and has excellent air-permeability and conductivity and, therefore, is expected to be used as a heat exchange material, a heat insulating material, a sound absorbing material, an impact absorbing material, a carrier of various chemical substances (catalyst and the like), a filter material, an electrode and a current collector of various cells, a gas channel of a fuel cell, an adsorbing material, an electromagnetic shielding material, and the like.

Examples of methods for producing the porous metal body include a method in which a foaming agent is added to a molten metal, agitation is performed and, thereafter, cooling is performed (precursor method) and a method in which a metal powder and a powder called a spacer are mixed and sintered and, thereafter, the spacer is removed (spacer method, for example, PTL 1).

The functionality of the porous metal body has attracted attention and a plurality of porous metal bodies having different functions have been stacked and integrated such that the resulting porous metal body has become multifunctional. Regarding the method for stacking a plurality of porous metal bodies, methods that are used include a method in which porous metal bodies are produced and, thereafter, these are bonded by an adhesive and a method in which integration is performed by sintering. Regarding the latter method, methods that are used include a method in which one of the porous metal bodies is produced by sintering, a paste containing another metal powder is stacked on the surface of the porous metal body and, thereafter, sintering is performed again and a method in which a forming die is filled with metal powders and the like in layers and, thereafter, sintering is performed (for example, PTL 2).

CITATION LIST Patent Literature

PTL 1: Japanese Unexamined Patent Application Publication No. 2013-82965

PTL 2: Japanese Unexamined Patent Application Publication No. 2005-29435

SUMMARY OF INVENTION Technical Problem

Regarding the method in which a plurality of porous metal bodies are stacked by using an adhesive, the air-permeability is easily impaired at an interface between the porous metal bodies. Also, there is a concern that the functionality of the porous metal body may be impaired and an inconvenience may occur in use at high temperatures because of intervention of substances other than the porous metal body. Regarding the method in which a plurality of porous metal bodies are integrated by sintering, it is very difficult to control the pore size and the porosity of each of the porous metal bodies.

Solution to Problem

An aspect of the present invention relates to a composite material including a first porous metal body having a three-dimensional mesh-like skeleton, a second porous metal body having a three-dimensional mesh-like skeleton, and a bonding portion formed by entanglement of the skeleton of the first porous metal body and the skeleton of the second porous metal body.

Another aspect of the present invention relates to a method for producing a composite material, in which a first porous metal body having a three-dimensional mesh-like skeleton is bonded to a second porous metal body having a three-dimensional mesh-like skeleton, the method comprising the steps of preparing a first porous metal precursor of the first porous metal body and a second porous metal precursor of the second porous metal body in a first step, arranging the first porous metal precursor and the second porous metal precursor such that the first porous metal precursor and the second porous metal precursor at least overlap one another in a second step, and pressing an overlap portion between the first porous metal precursor and the second porous metal precursor in a third step.

Advantageous Effects of Invention

According to the present invention, a composite material, in which a plurality of porous metal bodies are bonded to each other, can be provided without impairing the function of each of the plurality of porous metal bodies. Also, a method, in which a composite material produced by combining a plurality of porous metal bodies is very simply obtained, can be provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view schematically showing a composite material according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an example of the structure of part of a skeleton of a porous metal body.

FIG. 3 is a sectional view schematically showing a cross section of part of the skeleton shown in FIG. 2.

FIG. 4A is a sectional view schematically showing a composite material according to another embodiment of the present invention.

FIG. 4B is a sectional view schematically showing a composite material according to another embodiment of the present invention.

FIG. 4C is a sectional view schematically showing a composite material according to another embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS Description of Embodiment of Invention

Initially, the contents of an embodiment according to the present invention will be listed and described.

(1) A composite material according to the present invention includes a first porous metal body having a three-dimensional mesh-like skeleton, a second porous metal body having a three-dimensional mesh-like skeleton, and a bonding portion formed by entanglement of the skeleton of the first porous metal body and the skeleton of the second porous metal body. Consequently, a plurality of porous metal bodies are bonded without impairing the function of each of the porous metal bodies.

(2) The porosity of the first porous metal body may be different from the porosity of the second porous metal body. Meanwhile, (3) the first porous metal body may contain a metal different from a metal contained in the second porous metal body. Consequently, the composite material can become multifunctional.

(4) In addition, a method for producing a composite material, in which a first porous metal body having a three-dimensional mesh-like skeleton is bonded to a second porous metal body having a three-dimensional mesh-like skeleton, according to the present invention includes the steps of preparing a first porous metal precursor of the first porous metal body and a second porous metal precursor of the second porous metal body in a first step, arranging the first porous metal precursor and the second porous metal precursor such that the first porous metal precursor and the second porous metal precursor at least overlap one another in a second step, and pressing an overlap portion between the first porous metal precursor and the second porous metal precursor in a third step. Consequently, a composite material, in which a plurality of porous metal bodies are combined, can be produced by a very simple method.

Details on Embodiment of Invention

The embodiments according to the present invention will be specifically described below. In this regard, the present invention is not limited to the contents described below. The present invention is to be determined by the appended claims and is intended to cover all modifications within the spirit and scope of the claims or the equivalents thereof.

The composite material will be described below with reference to FIGS. 1 to 3. FIG. 1 is a sectional view schematically showing an embodiment of the composite material. FIG. 2 is a schematic diagram showing an example of the structure of part of a skeleton of a porous metal body. FIG. 3 is a sectional view schematically showing a cross section of part of the skeleton.

Composite Material

A composite material 10 includes a first porous metal body 1 a having a three-dimensional mesh-like skeleton 102 and a second porous metal body 1 b having a three-dimensional mesh-like skeleton 102. The first porous metal body 1 a is bonded to the second porous metal body 1 b, and the skeletons thereof are entangled with each other in the bonding portion 2.

In other words, the skeletons of the first porous metal body 1 a and the second porous metal body 1 b are entangled with each other and, thereby, the first porous metal body 1 a is bonded to the second porous metal body 1 b.

The first porous metal body 1 a and the second porous metal body 1 b have, for example, a nonwoven fabric-like structure or a spongy structure. Such a structure has holes and a metal skeleton. For example, a porous metal body having the spongy structure is composed of a plurality of cells having a hole and a metal skeleton. As shown in FIG. 2, one of cells can be expressed as a regular dodecahedron, for example. A hole 101 is demarcated by a fibrous or rod-like metal portion (fiber portion 102), and a plurality of holes are three-dimensionally connected to each other. The skeleton of the cell is formed by connection of the fiber portions 102. The cell includes substantially pentagonal openings (or windows) 103 surrounded by the fiber portions 102. The adjacent cells are communicated with each other by sharing one opening 103. That is, the skeleton of each porous metal body is formed by fiber portions 102 that form a mesh-like network while demarcating a plurality of holes 101 continued. The skeleton having such a structure is called a three-dimensional mesh-like skeleton.

As shown in FIG. 3, the fiber portions 102 may have a cavity 102 a in the inside, that is, may be hollow. A porous metal body having a hollow skeleton is very lightweight while having a bulky three-dimensional structure.

The configurations of the first porous metal body 1 a and the second porous metal body 1 b may be the same or different from each other. The configuration of the porous metal body is determined in accordance with the type of the metal, the porosity, the thickness, and the like as described below. In the case where the configurations of the porous metal bodies are the same, a large (large-area or thick) composite material that is not easily produced from the viewpoint of equipment or cost can be obtained by connecting the two. Even in the case where the configurations of the porous metal bodies are the same, each of the porous metal bodies can have a function different from each other by the hole 101 of each of the porous metal bodies being filled with a substance different from each other. In the case where the configurations of the first porous metal body 1 a and the second porous metal body 1 b are different from each other, there is an advantage that the porous metal bodies can have functions, e.g., air-permeability, different from each other.

The holes 101 of the porous metal bodies may be filled with various substances, e.g., a catalyst, an adsorbing agent, an electrode active material, and an electrolyte. Consequently, the composite material 10 can be provided with various functions. The substances introduced into the holes 101 of the porous metal bodies may be the same or different from each other.

In the bonding portion 2 of the composite material, the skeletons of the first porous metal body 1 a and the second porous metal body 1 b are entangled with each other. Entanglement of skeletons with each other may refer to, for example, a state in which the vicinity of an end portion of the fiber portion 102 of the second porous metal body 1 b has entered the opening 103 located in the vicinity of an end portion of the first porous metal body 1 a. Also, entanglement of skeletons may be a state in which fiber portions 102 present in the vicinity of end portions of the porous metal bodies are plastically deformed and are engaged with each other. Consequently, the first porous metal body 1 a and the second porous metal body are firmly bonded to each other in the vicinity of the respective principal surfaces without interposing an adhesive therebetween. As a result, the first porous metal body 1 a and the second porous metal body 1 b also communicate with each other. Such a composite material has excellent permeability of a fluid and, thereby, is suitable for, for example, carriers of various chemical substances, various filters, and gas channels of fuel cells.

The metal that constitutes each of the porous metal bodies may be appropriately selected in accordance with the application and the use environment. In the composite material, the porous metal bodies are bonded to each other by using the skeletons thereof. Therefore, there is no particular limitation regarding the type of a metal used. That is, the metals constituting the first porous metal body 1 a and the second porous metal body 1 b may be the same or different from each other. Examples of the above-described metals include copper, a copper alloy (alloy of copper and, for example, Fe, Ni, Si, or Mn), nickel or a nickel alloy (alloy of nickel and, for example, tin, chromium, or tungsten), aluminum or an aluminum alloy (aluminum and, for example, Fe, Ni, Si, or Mn), and a stainless steel.

The porosity (percentage of voids) of the composite material 10 is not specifically limited and may be appropriately selected in accordance with the application. The porosity is, for example, 60 percent by volume or more, preferably 70 percent by volume or more, and further preferably 85 percent by volume or more. The porosity is less than 100 percent by volume, preferably 99.5 percent by volume or less, and further preferably 99 percent by volume or less. These lower limit values and upper limit values can be appropriately combined. The porosity can be determined by {1−(apparent specific gravity of porous metal body/true specific gravity of metal)}×100.

The porosities of the porous metal bodies are not specifically limited and may be set such that the porosity of the entire composite material becomes, for example, within the above-described range. The first porous metal body 1 a and the second porous metal body 1 b communicate with each other in the bonding portion 2. Therefore, the porosity of the composite material 10 well reflects each of the porosities of the first porous metal body 1 a and the second porous metal body 1 b. In other words, if the porosities of the first porous metal body 1 a and the second porous metal body 1 b are known, the porosity of the composite material 10 can be easily controlled. Further, as described later, the porosity of the composite material 10 can be predicted from the thicknesses and the porosities of the porous metal bodies before bonding (precursors).

The porosities of the porous metal bodies are, for example, within the same range as the porosity of the composite material 10. The porosities of the porous metal bodies may be the same or different from each other. In the case where the porosities of the porous metal bodies are different from each other, the composite material 10 is particularly suitable for various filter materials and gas channels of fuel cells.

The average hole size V of the holes 101 of each of the porous metal bodies is not specifically limited and may be appropriately selected in accordance with the application. For example, the average hole size V may be 300 to 5,000 μm and be 400 to 3,500 μm. The average hole sizes V of the holes 101 of the porous metal bodies may be the same or different from each other.

The average hole size V1 is determined as described below, for example. Initially, an arbitrary hole 101 a is selected among holes 101 in a porous metal body. The diameter of a maximum sphere that is enclosed in the hole 101 a and the diameter of a minimum sphere S that can enclose the hole 101 a (refer to FIG. 2) are measured and the average value thereof is determined. This is assumed to be the hole size Va of the hole 101 a. Likewise, the hole sizes Vb to Vj of a plurality of (for example, nine) other arbitrary holes 101 b to 101 j included in the porous metal body are determined, and the average value of the hole sizes Va to Vj of the 10 holes 101 a to 101 j is assumed to be the hole size V1.

The average size (pore size D) of openings 103 of each of the porous metal bodies is not specifically limited and may be appropriately selected in accordance with the application. The pore sizes D of the porous metal bodies may be, for example, 100 to 3,000 μm, or be 200 to 2,000 μm. The pore sizes D of the porous metal bodies may be the same or different from each other.

The pore size D is determined as described below, for example. Initially, an arbitrary opening 103 a is selected among openings 103 in a porous metal body. The diameter of a maximum perfect circle C (refer to FIG. 2) that is enclosed in the opening 103 a and the diameter of a minimum perfect circle that can enclose the opening 103 a are measured and the average value thereof is determined. This is assumed to be the pore size Da of the opening 103 a. Likewise, the pore sizes Db to Dj of a plurality of (for example, nine) other arbitrary openings 103 b to 103 j included in the porous metal body are determined, and the average value of the pore sizes Da to Dj of the 10 openings 103 a to 103 j is assumed to be the pore size D. Specifically, in a SEM photograph of the principal surface of the porous metal body, a region R that includes at least 10 openings 103 entirely is determined. For example, 10 openings are selected at random among openings 103 included in the region R, and pore sizes Da to Dj of the openings 103 a to 103 j are calculated by the above-described method. The average value of the calculated pore sizes Da to Dj of the openings 103 a to 103 j is assumed to be the pore size D. In this regard, the average hole size V and the pore size D of each of the porous metal bodies can be predicted from the porous metal body before bonding (precursor).

The specific surface area (BET specific surface area) of the composite material 10 is not specifically limited and may be appropriately selected in accordance with the application. The specific surface area of the composite material 10 may be, for example, 100 to 9,000 m²/m³ or 200 to 6,000 m²/m³. The specific surface areas of the porous metal bodies are not specifically limited and may be set such that the specific surface area of the composite material becomes, for example, within the above-described range. The specific surface areas of the porous metal bodies may be the same or different from each other.

The widths Wf of the skeletons 102 of each of the porous metal bodies are not specifically limited. In particular, from the viewpoint of bonding strength, the average value of the width Wf is preferably 100 to 1,000 μm, and more preferably 100 to 500 μm. The widths Wf of the skeletons 102 of the porous metal bodies may be the same or different from each other.

The density (cell density) of openings 103 of each of the porous metal bodies are not specifically limited and may be appropriately selected in accordance with the application. The cell density of each of the porous metal bodies may be, for example, 5 to 150 every 2.54 cm or 5 to 70 every 2.54 cm. The cell densities of the porous metal bodies may be the same or different from each other.

The thickness of the composite material 10 is not specifically limited and may be appropriately selected in accordance with the application. The thickness of the composite material 10 is, for example, 0.1 mm or more or may be 3 mm or more. Meanwhile, the thickness of the composite material 10 is, for example, 50 mm or less. The thickness of each of the porous metal bodies is not specifically limited and may be set such that the thickness of the composite material becomes, for example, within the above-described range. The thicknesses of the porous metal bodies may be the same or different from each other. The thickness of each of the porous metal bodies is, for example, 0.05 mm or more, may be 0.8 mm or more, or may be 1 mm or more. Meanwhile, the thickness of each of the porous metal bodies is, for example, less than 50 mm and may be 20 mm or less.

For example, in the case where the composite material 10 is used for a carrier of a catalyst, a plurality of porous metal bodies described below may be used. Examples of the first porous metal body 1 a include a porous metal body having an average hole size of the holes 101 of 2,000 to 4,000 μm, a specific surface area of 400 to 600 m²/m³, a cell density of 6 to 10 every 2.54 cm, and a thickness of 5 to 10 mm. Examples of the second porous metal body 1 b include a porous metal body having an average hole size of the holes 101 of 450 to 550 μm, a specific surface area of 6,500 to 8,500 m²/m³, a cell density of 48 to 52 every 2.54 cm, and a thickness of 5 to 10 mm. Consequently, the composite material 10 can be provided with a function suitable for a catalyst carrier.

The configuration of the composite material 10 is not limited to the configuration in which the entire surface of one principal surface of the first porous metal body 1 a is bonded to the entire surface of one principal surface of the second porous metal body 1 b, as shown in FIG. 1. For example, as shown in FIG. 4A, part of one principal surface of the first porous metal body 1 a may be bonded to part of one principal surface of the second porous metal body 1 b. In this case, the bonding portion 2 may be formed on an end surface of the first porous metal body 1 a and an end surface of the second porous metal body 1 b.

Alternatively, as shown in FIG. 4B, a composite material 10B may have a three-layer structure in which the entire surface of one principal surface of a third porous metal body 1 c is further bonded to the entire surface of the other principal surface of the second porous metal body 1 b. In this case, the bonding portions 2 may be formed between the first porous metal body 1 a and the second porous metal body 1 b (bonding portion 2 ab) and between the second porous metal body 1 b and the third porous metal body 1 c (bonding portion 2 bc). In addition, 4 layers or more of porous metal bodies may be bonded.

Further, as shown in FIG. 4C, in a composite material 10C, the entire surface of one principal surface of the first porous metal body 1 a may be bonded to the entire surface of one principal surface of the second porous metal body 1 b with a third porous metal body 1 c and a fourth porous metal body 1 d, which are arranged side by side, interposed therebetween. In this case, the bonding portions 2 may be formed between the first porous metal body 1 a and the third porous metal body 1 c (bonding portion 2 ac), between the first porous metal body 1 a and the fourth porous metal body 1 d (bonding portion 2 ad), between the second porous metal body 1 b and the third porous metal body 1 c (bonding portion 2 bc), and between the second porous metal body 1 b and the fourth porous metal body 1 d (bonding portion 2 bd). The configuration of the composite material 10 may be a combination of the above-described configurations.

Method for Producing Porous Metal Body

Each of the porous metal bodies can be formed by, for example, covering a resin porous body with the above-described metal. Covering with the metal can be performed by plating treatment, a vapor phase method (evaporation, plasma chemical vapor deposition, sputtering, or the like), covering with a metal paste, or the like. A three-dimensional mesh-like skeleton is formed by the covering treatment with a metal. Among these covering methods, the plating treatment is preferable.

The plating treatment has to form a metal layer on the surface of a resin porous body (including a surface facing inner voids) and known plating methods, e.g., an electroplating method, and a molten salt plating method, can be adopted. A three-dimensional mesh-like porous metal body in accordance with the shape of the resin porous body is formed by the plating treatment. In this regard, in the case where the plating treatment is performed by electroplating, it is desirable that a conductive layer be formed before the electroplating is performed. The conductive layer may be formed on the surface of the resin porous body by conductive agent coating or the like other than electroless plating, evaporation, sputtering, and the like, or may be formed by dipping a resin porous body into a dispersion containing a conductive agent.

There is no particular limitation regarding the resin porous body as long as voids are included, and a resin foam, a resin nonwoven fabric, and the like can be used. In particular, a resin foam is preferable because communicating holes are easily formed. Regarding the resin that constitutes these porous bodies, after the metal covering treatment, preferably, the inside of the skeleton 102 can be made hollow by decomposition or dissolution while the shape of the three-dimensional mesh-like skeleton of the metal is maintained. Examples can include thermosetting resins, e.g., a thermosetting polyurethane and a melamine resin; and thermoplastic resins, e.g., an olefin resin (polyethylene, polypropylene, and the like) and a thermoplastic polyurethane. In particular, it is preferable that a thermosetting polyurethane and the like be used from the viewpoint of ease of formation of holes having more uniform sizes and shapes.

It is desirable that the resin in the skeleton be decomposed or dissolved by heat treatment or the like and, thereby, be removed. After the heat treatment, components (a resin, a decomposition product, an unreacted monomer, an additive contained in the resin, and the like) remaining in the skeleton may be removed by washing or the like. The resin may be removed by performing heat treatment while a voltage is appropriately applied, as necessary. In this regard, the heat treatment may be performed in the state, in which a porous body subjected to plating treatment is dipped in a molten salt plating bath, while a voltage is applied.

In the case where the inside resin is removed after the metal covering treatment, as described above, a cavity is formed inside the skeleton of the porous metal body and the skeleton becomes hollow. The thus produced porous metal body includes a skeleton having a three-dimensional mesh-like structure in accordance with the shape of the resin foam. Regarding the commercially available porous metal body, “Aluminum-Celmet” (registered trademark) and “Celmet” (registered trademark) of copper or nickel, produced by Sumitomo Electric Industries, Ltd., can be used.

Method for Producing Composite Material

The composite material 10 can be produced by a very simple method in which, for example, a plurality of porous metal bodies are stacked and, thereafter, pressing is performed. Specifically, the composite material 10 is produced by a method including a first step of preparing a precursor (first porous metal precursor P1 a) of the first porous metal body 1 a and a precursor (second porous metal precursor P1 b) of the second porous metal body 1 b, a second step of arranging the first porous metal precursor P1 a and the second porous metal precursor P1 b such that these at least overlap one another, and a third step of pressing an overlap portion between the first porous metal precursor P1 a and the second porous metal precursor P1 b.

First Step

In the first step, the first porous metal precursor P1 a and the second porous metal precursor P1 b are prepared. The first porous metal precursor P1 a and the second porous metal precursor P1 b are made into the first porous metal body la and the second porous metal body 1 b, respectively, through the third step (pressing).

The skeletons of portions other than the overlap portion between the first porous metal precursor P1 a and P1 b may be deformed by pressing. Therefore, the porosities, the pore sizes, and the average hole sizes of the first porous metal precursor P1 a and the second porous metal precursor P1 b may change between before and after the pressing. However, changes in the porosities, the pore sizes, and the average hole sizes due to the pressing can be predicted on the basis of an empirical rule. For example, each of the porosities, the pore sizes, and the average hole sizes of the first porous metal precursor P1 a and the second porous metal precursor P1 b may be reduced by 5% to 90% due to the pressing. That is, the porosities, the pore sizes, and the average hole sizes of the first porous metal precursor P1 a and the second porous metal precursor P1 b may be appropriately set such that the porosities, the pore sizes, and the average hole sizes of the first porous metal body 1 a and the second porous metal body 1 b after the pressing become within predetermined ranges, and precursors that satisfy the above-described condition may be selected. According to the present embodiment, the chemical properties and the physical properties of each of the precursors are hardly changed and, therefore, a predetermined composite material can be produced by a very simple method as described above.

The holes of the first porous metal precursor P1 a and the second porous metal precursor P1 b may be filled with the above-described various substances. The substances introduced into the precursors may be the same or different from each other. For example, in the case where holes are filled with substances different from each other before bonding, the composite material 10 can be provided with various functions. The precursors are bonded by a very simple method, that is, only performing pressing, and as a result, the functions of the substances introduced are not easily impaired.

Second Step

In the second step, the first porous metal precursor P1 a and the second porous metal precursor P1 b are arranged such that the two at least overlap one another. The arrangement method is not specifically limited and the arrangement may be performed such that the composite material 10 has a structure shown in FIG. 1, FIGS. 4A to 4C, or has a configuration in which these structures are combined. Bonding is caused in the overlap portion between the first porous metal precursor P1 a and the second porous metal precursor P1 b by pressing, which is performed later, so as to form the bonding portion 2.

Third Step

In the third step, at least the above-described overlap portion is pressed. Consequently, the metal skeleton (fiber portion 102) of the overlap portion of at least one precursor is plastically deformed and, as a result, the porous metal bodies are firmly bonded to each other. It is not necessary that the skeletons of both the precursors be plastically deformed. Part of the skeleton of one precursor may be plastically deformed so as to enter the opening 103 of the other. Alternatively, parts of skeletons of both the precursors may be plastically deformed and become entangled while engaging with each other. Each of the porous metal bodies has a three-dimensional mesh-like skeleton and, therefore, is plastically deformed and has appropriate elasticity. As a result, the porous metal body is not easily damaged even when pressing is performed.

In the case where the porous metal bodies are formed of a sintered body of a metal powder, it is difficult to bond the two by pressing. This is because the sintered body is not easily plastically deformed and may be broken due to pressing.

There is no particular limitation regarding the pressing method, and examples thereof include roll press and flat press.

Pressing may be performed under heating. In particular, it is preferable that bonding be performed by roll press at ambient temperature from the viewpoint of cost and production efficiency. The press pressure is not specifically limited and may be appropriately set in consideration of the easiness of plastic deformation of the precursors. The press pressure may be, for example, 10 kPa or more, or 100 kPa or more. Meanwhile, the press pressure may be 4,000 kPa or less, or 5,000 kPa or less.

INDUSTRIAL APPLICABILITY

The composite material according to the present invention has excellent permeability of a fluid and, therefore, is suitable for, for example, carriers of various chemical substances, various filters, and gas channels of fuel cells. Also, the composite material is expected to become multifunctional and, therefore, can be applied to various uses including a porous metal body.

REFERENCE SIGNS LIST

1 a: first porous metal body, 1 b: second porous metal body, 1 c: third porous metal body, 1 d: fourth porous metal body, 2, 2 aa, 1 ac, 2 ad, 2 bc, 2 bd: bonding portion, 10, 10A to 10C: composite material 10, 101: hole, 102: skeleton, 102 a: hollow portion, 103: opening 

1. A composite material comprising: a first porous metal body having a three-dimensional mesh-like skeleton; a second porous metal body having a three-dimensional mesh-like skeleton; and a bonding portion formed by entanglement of the skeleton of the first porous metal body and the skeleton of the second porous metal body.
 2. The composite material according to claim 1, wherein the porosity of the first porous metal body is different from the porosity of the second porous metal body.
 3. The composite material according to claim 1, wherein the first porous metal body contains a metal different from a metal contained in the second porous metal body.
 4. A method for producing a composite material, in which a first porous metal body having a three-dimensional mesh-like skeleton is bonded to a second porous metal body having a three-dimensional mesh-like skeleton, the method comprising the steps of: preparing a first porous metal precursor of the first porous metal body and a second porous metal precursor of the second porous metal body in a first step; arranging the first porous metal precursor and the second porous metal precursor such that the first porous metal precursor and the second porous metal precursor at least overlap one another in a second step; and pressing an overlap portion between the first porous metal precursor and the second porous metal precursor in a third step. 